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Processing of influenza HA protein in MDCK cells: components with different mobilities in polyacrylamide gel
Abstract:
In influenza virus-infected MDCK cells labelled with 14C-chlorella hydrolysate or 35S-methionine a virus-specific protein component is revealed migrating slightly faster than HA protein in polyacrylamide gel electrophoresis. Under chase conditions the component disappears either completely or partially, with a concomitant intensification of the HA band. The rate and extent of this transition are strain-dependent. Both the HA band and the faster moving component are not revealed if the cells are labelled in the presence of 20 mM of D-glucosamine. In primary cell cultures of chick embryos a single HA band with a mobility similar to that of the faster moving component in MDCK cells has been observed. It is suggested that the transition of the label from the faster moving component to the HA band reflects the final step of HA processing specific for MDCK cells.
Insights
Researchers identified a precursor protein that transforms into influenza virus hemagglutinin (HA) in MDCK cells. This HA processing is strain-dependent and inhibited by D-glucosamine, suggesting a final maturation step.
Area of Science:
- Virology
- Cell Biology
- Biochemistry
Background:
- Influenza virus hemagglutinin (HA) is crucial for viral entry and is a major target for vaccines.
- Understanding HA protein processing is essential for comprehending influenza virus replication and pathogenesis.
Purpose of the Study:
- To investigate the post-translational processing of influenza virus HA protein in MDCK cells.
- To identify any intermediate or precursor protein forms involved in HA maturation.
Main Methods:
- Influenza virus-infected MDCK cells were metabolically labeled with radioactive isotopes (14C-chlorella hydrolysate or 35S-methionine).
- Pulse-chase experiments were performed to track protein transitions using polyacrylamide gel electrophoresis (PAGE).
- Experiments included labeling in the presence of D-glucosamine and analysis in primary chick embryo cell cultures.
Main Results:
- A virus-specific protein component migrating faster than mature HA was detected in MDCK cells.
- This faster-migrating component diminished over time, with a corresponding increase in the HA band intensity during chase periods.
- The transition rate and extent varied depending on the influenza virus strain.
- D-glucosamine treatment prevented the appearance of both the faster-migrating component and the HA band.
- Primary chick embryo cells showed a single HA band with mobility similar to the faster-migrating component observed in MDCK cells.
Conclusions:
- The faster-migrating component likely represents a precursor to the mature HA protein.
- The observed transition suggests a final processing step for HA maturation specific to MDCK cells.
- D-glucosamine interferes with this final HA processing step, highlighting its importance.